I had previously seen what we in the UK usually call the 'Grass Snake' in the wilder areas of a local park. But still, I was surprised in late July 2020 to find one in my garden. I saw it quite often, until into October 2020, so hopefully it has found a place to hibernate nearby and will appear again in 2021. See at the bottom of this page for a clarification of which type of snake we are talking about, and its naming.
My first sighting of the snake, inside an out-building. I was initially very surprised to see it, among garden canes and tools, and didn't get a clear view, so I quickly checked up on the distinguishing features of Grass Snakes, just to make sure this wasn't an escaped captive snake of some other kind.
Now convinced that it was indeed a non-poisonous grass snake, I got this photo, showing the yellow band behind the head, and black markings along the body. Despite not being a snake that bites humans, it still put on a 'threatening' display, with hissing and an aggressive posture.
Date: 2020 August 9
The next sighting: there was a rush of activity on the patio, just outside the door to the house - the snake was chasing a frog, which it duly caught. In the first photo, the snake has the head end of the frog in its mouth. It's difficult to work out what you're looking at, but both the frog's back legs are visible, and one front leg.
The second photo is 9 minutes later, by which time the snake has swallowed most of the frog.
In the pond. Some people say that this snake could better have been named the 'water snake' instead of 'grass snake'. It is often found in or near water, and swims well - maybe not surprising for a creature which has amphibians (frogs and toads) as a major part of its diet. I often saw the snake in the garden pond.
The 'grass snake' which occurs in the UK (and elsewhere) was, until around 2017, considered to be a sub-species of the European Grass Snake, with latin name Natrix natrix ssp. helvetica. Around 2017, new research (see e.g. here) resulted in the latin name being changed to Natrix helvetica ssp. helvetica, and occasional use of the 'common name' "Barred Grass Snake". Unfortunately, the media's typically poor reporting of science led to headlines saying that a new snake had been discovered in the UK - no, just a changed name for the same snake. As well as this one, there are just two other types of snake present in the UK: the 'Adder' Vipera berus; and the 'Smooth Snake' Coronella austriaca.